I replaced my PS2 laser because it had problems reading DVDs but after running the lens changer program 4 TIMES it still has the same problem, the only thing I could think
Tweak3D.net - How to Repair a Malfunctioning Playstation 2; Fix Disc Read Errors
If your PS2 fat reads blue and black discs, but won't read or is slow to read DVDs...and cleaning laser doesn't work.....DONT buy a new laser. Just do this in small increments
How to clean the laser in a PS2
Playstation 2 (fat): Laser cleaning and / or replacement - Dreamcast.nu